1. Field of the Invention
This invention relates to a resonating device, and more particularly, to an improved quartz crystal resonator and machine for an improved quartz crystal resonator.
2. Description of the Prior Art
In the prior art, quartz crystal resonators adapted to resonate in the thickness shear mode of vibration at fundamental frequencies have been reliably constructed for operation at frequencies as high as twenty-five megaHertz. In order to make resonators that operate at fundamental frequencies higher than twenty-five megaHertz, the quartz wafer becomes increasingly thinner resulting in a number of problems. First of all, the major surfaces of the quartz wafer must be precisely flat and parallel or there will be several portions of the wafer that tend to resonate causing spurious responses. The thinness of the quartz wafer makes it very fragile and subject to breakage during handling and manufacture. The thin wafer is also very difficult to mount and securely support such that it is not damaged during normal usage.
Another way to obtain frequencies higher than twenty-five megaHertz is to operate a quartz crystal resonator at the third harmonic of its fundamental frequency. Theoretically, a quartz wafer can resonate at odd harmonics of its fundamental frequency, but harmonic operation is difficult to achieve since the quartz wafer has a strong propensity to oscillate at its fundamental frequency. Thus, odd harmonic operation of the quartz wafer is difficult to achieve and requires more complex oscillator circuitry than for fundamental operation. Also, the delta-f-parameter (frequency shift resulting from circuit impedance change) is much more easily maximized and controlled with a fundamental crystal. This is an important consideration in modulating and tuning an oscillator.
For the foregoing and other shortcomings and problems, there has been a long felt need for an improved quartz crystal resonator.